Vulnerable
by Revhead
Summary: Set after 11x11 *SPOILERS*. Dean is more vulnerable than he realises and unfortunately, Lucifer knows his weakness. WARNINGS: Slash, Graphic, Dub-con. Destifer.


**Vulnerable**

Dean couldn't sleep.

His head hurt and he could still hear a faint ringing in his ears, but a concussion was nothing new to him. As head injuries went, this was one of the mildest he'd had and he knew that after a good night's rest he would be fine.

Problem was that he couldn't sleep.

Banshees were supposed to go after people who were vulnerable. Dean knew that some chicks dug sensitive guys, so he had played the 'vulnerable' card a few times to get laid, but it was not a word he would typically use to describe himself. He was a hunter, a soldier, born and raised. Vulnerability was not in the job description, and no matter what he had been through he took pride in the way he faced his problems head on.

Trouble was that lately… he felt like he wasn't in control.

Amara had talked about destiny. She had kissed him and then said that they were destined to be together. She said it was inevitable.

But Dean didn't believe in destiny. He was supposed to be 'destined' to be Michael's vessel, but he had said no. He was supposed to be 'destined' to end the apocalypse, but Sam had saved the world in his place. They had thrown out the script and written their own story, for better or for worse. He refused to let his life be dictated by some higher power.

But Amara had said that she couldn't be resisted. And Dean was afraid that she was right.

He couldn't stop thinking about her. He wanted to find her, to be with her, to taste her lips again. It wasn't even lust for the body she had grown into – he was _drawn_ to her. He longed to be in her presence, to submit to anything she would ask of him.

With each passing day, the pull grew stronger. The banshee case was supposed to distract him but she was always there in the back of his mind, taunting him, tempting him.

 _You and I will be together. We will become one._

The thought sickened him. She was an ancient evil, a malevolent god bent on the destruction of the universe her brother had created, and he'd blown both chances he'd had of killing her. Because she made him _feel_ something, something he couldn't understand… and he couldn't seem to resist no matter how hard he tried.

He couldn't tell Sam. He knew that it would only freak his brother out and Sam would probably feel the need to bench him, take him off the hunt to keep him well out of Amara's reach. But she was a god, and there was nowhere on Earth that he could hide from her. When she came for him there would be nothing he could do. His only hope was to find some way to kill her first… or some way for Sam or Cas to kill her because experience had shown that he didn't have the gumption to do it himself.

Cas was working on it. He had been in here, looking for a way to draw Amara out. Good old Cas, always ready and willing to give a helping hand when the world was ending for the umpteenth time.

Only… there had been something off about him.

Troubled, Dean gave up on the idea of sleep and rolled into a sitting position. He stared at the wall, recalling every detail of the strange encounter.

He had entered the bunker and immediately warning bells had gone off in his head. His hunter's instincts had warned him that there was an intruder… but it had only been Cas. That in itself was odd – after years of surprise visits, often in awkward circumstances, Dean had learned what the air felt like when Cas was around and the vibes in the bunker had been all wrong. Still, maybe he could chalk it up to feeling a little off himself.

But the archive room Cas was ransacking had been a total mess and that was strange too. Cas had a great deal of respect for the Men of Letters, was meticulously neat and knew better than to disturb Sam's filing system. Not to mention the fact that he had known full well that Sam and Dean had been through these files with a fine-toothed comb looking for even the faintest trace of data on the Darkness and what little they had found was currently stored in the Active Files that they kept in the library. But maybe as an angel he thought he would see something they missed. It was possible.

He was probably over-thinking things. It didn't mean anything that Cas hadn't been wearing his trench coat.

But even as Dean was confiding in his friend, as he ever had, revealing truths that he wasn't even comfortable sharing with Sam he had felt… uneasy.

Maybe it was because talking about the twisted up emotions he felt for Amara made him uneasy. Maybe it was the way Cas had said "Attraction?", or the way that he had looked at him when Dean's silence said more than words could.

He couldn't understand why the reassuring words and the hand on his shoulder had sent a shudder through him.

Maybe it was because a part of him had been hoping for a different reaction.

…jealousy?

No. He was being ridiculous.

But it hadn't felt like Cas – because the angel's touch usually sent a mixed bolt of pleasure and anxiety through him and this time all he had felt was cold.

It had scared him. God help him it had scared him because the feelings for Amara were bad enough without taking away the feelings he had for… when he… when Cas…

Dean buried his head in his hands and scraped his fingers through his hair. He couldn't afford to think like this.

He was the one messed up. Cas was fine. He should grab a drink and the go to sleep and pretend none of this had ever crossed his mind.

He stood up, crossed the room and opened the door –

Only to find Cas standing on the other side, hand poised to knock.

Dean stumbled back. " _Jesus_ , Cas, you scared me!"

Cas dropped his hand awkwardly. "Sorry. I was just coming to see if you were alright."

"I'm fine."

"You're wounded," Cas argued, reaching to examine the cut on Dean's forehead.

Dean flinched away from his touch. "It's fine. I just bumped my head."

"More than once. It was the banshee; she got to you. Dean how could you let her in like that?"

"I didn't mean to!" Dean wheeled away, knowing he was not in any state of mind to have a coherent conversation right now but the words kept spilling out anyway. "My walls aren't holding up like they used to. Lately all manner of things seem to be worming their way inside my brain and I don't know how to stop it."

"You mean Amara. Dean, I told you we would figure this out together."

Dean turned to pin Cas with an accusing glare. "How can we? You keep pulling the disappearing act on me."

Cas tilted his head, looking at him thoughtfully. "You want me to… stay?"

Dean swallowed. "Well… yeah. Three heads are better than two. We could use your help."

"Is that all?"

Dean frowned. "What do you mean?"

"You just want me to help you find and kill Amara. That's the only reason you want me around?"

"Cas – no, it's not like that, I just – what are you trying to say?"

Cas stepped into the room and closed the door behind him. "You can be honest with me, Dean. If I'm just a soldier to you, that's fine. I'm used to being considered expendable and it won't change my dedication to the mission-"

"No! Cas. Of course I don't think – I know you're not a hammer. We established that way back at the beginning, remember? After all this time I would have thought that you knew how I… I mean, I know I haven't really said it in so many words, but I thought you knew that I consider you… a friend. You're my friend. My best friend, as a matter of fact."

"That's nice of you to say, Dean."

Dean coughed awkwardly. "So no more of this talk about being a soldier, or expendable or whatever. If there wasn't a war going on I'd still want you here. We could… I don't know. Relax. Drink a few beers. Watch Netflix and-"

"Chill?"

Dean choked. "Uh- that's not what I-"

"Dean, are you sure you are alright? You're perspiring and your skin is very flushed."

"Yeah, I just – it's hot in here."

Cas nodded slowly. "Yes it is." He slid off his jacket, laid it on Dean's bed and loosened his tie.

Dean swallowed and tried very hard not to notice that those top few buttons of his shirt were undone. "Um, look Cas. It's late and I'm kinda tired."

"Of course. You need sleep." But he made no move to leave.

"Uh, Cas?"

Cas raised an eyebrow. "You wanted me to stay."

"Right. But not… not in here. There's another room down the hall you can use, if you want."

But Cas just took another step forward. "I like it in here. You've made it feel very… homey."

"Cas-"

"You know, Dean, you're not a very good liar. You called me a friend, but that's not what you think of me. Or at least, it's not what you want from me."

"What are you-"

Cas closed the distance between them, encroaching on Dean's personal space in a way that was very deliberate.

"I can tell how conflicted you are, Dean. A part of you knows what you really want, but you're afraid to admit it even to yourself. But you can't deny your feelings forever. Why won't you just give in?"

"Amara is evil. What I feel for her… it isn't real."

"No it isn't. But this is."

And without another word of warning, Cas leaned in to press a kiss to Dean's lips.

Dean jerked away. "What the hell, Cas?"

Cas took hold of his shoulders to stop him retreating any further and looked him square in the eyes. "I'm an angel, Dean. I was the one who gripped you tight and raised you from perdition. I have seen your soul laid bare and I know you better than anyone else does. I have known how you feel about me for years, but I was going to wait patiently until you worked up the courage to do something about it. Only now, circumstances have forced my hand."

"Cas, I have no idea what you're talking about."

"Amara wants you. You were branded with her mark and she thinks that gives her the right to claim you as her own. She is not the first to make such a brash assumption; Heaven once thought the same. But they forget, I marked you _first._ I would not let Heaven take you, just as I will not allow Amara to take you."

Cas shifted his hands to cup Dean's face and leant in.

Dean stared, wide-eyed, but he found he couldn't move. And when those lips pressed against his own for the second time, he was helpless to resist.

Cas made a pleased sound when Dean made no effort to push him away and tilted Dean's head to get a better angle. His tongue darted out and licked at the seam of Dean's mouth. When Dean's lips parted obediently, instinctively, Cas didn't hesitate. He thrust his tongue in deep and wrestled Dean's own into submission. He seemed to be trying to map out every inch of Dean's mouth and plunge down his throat at the same time and Dean was drowning in it but he wanted _more._

He tugged at Castiel's tie and flung it blindly to the floor. He fumbled with buttons for a few seconds before giving up and just ripping the shirt open. The taste of skin against his fingertips was bliss; he scrabbled down the firm chest and sculptured muscles, felt out the hollows of his hips and then finally reached the object of his search.

Cas groaned into his mouth as Dean palmed him; Dean took that as permission and wrenched at the belt that kept him from his prize.

Cas broke the kiss and for a second Dean thought he had gone too far, but then Cas was tugging at Dean's own shirt and seconds later they were pressed together, skin against skin, intense heat burning between them. Dean sought Castiel's lips again but captured them only for an instant before Cas had shoved him away.

He landed on the bed, sprawled out, staring helplessly up at his angel. He had half a moment to feel suddenly insecure under that intense gaze before Cas was on top of him, tearing away the last thin layer of clothing that kept them apart.

Flesh against flesh. It should have felt wrong, should have shocked some sense into him, but Dean bucked into the sensation with the desperation of a madman. Cas pinned his arms to the mattress and thrust back against him just as hard. The friction was intense and painful and the best thing Dean had ever felt in his entire life until an instant later when Cas wrapped a spit-slicked hand around both of them and began to pump.

Dean gave an inarticulate yell as arousal sparked through him, sharper than anything he had ever experienced before, but Cas only pumped harder and impossibly the pressure kept building. Dean had never let his imagination run this far but somewhere in the back of his mind he'd had half an inkling that if this ever happened it would be the other way around – Cas would be awkward and unsure but oh so yielding and Dean would be gentle and reassuring even as he fucked Cas into the mattress.

But this was not the shy and uncertain young angel that had panicked at a brothel. Cas was definitely the one in charge and Dean didn't mind, couldn't mind. It felt too damn good.

He wasn't going to last long. Cas was driving this thing hard and fast and Dean could feel that they were reaching a crescendo – until Cas suddenly pulled his hand away and raised his hips

Dean bucked, trying to re-establish the connection but Cas shoved his hips back down. Large, rough hands pushed Dean's legs apart, forcing them to spread wide, and then lifted them up over broad shoulders. Dean didn't have enough time to panic before two slicked-up fingers were pushing into his entrance.

It burned and he tried to pull back but the fingers just shoved in deeper and something sparked inside him, sending a sudden jolt of pleasure through his body that drowned out the pain. The fingers flexed and stretched within him, forcing him open wider, and then another finger joined. Cas thrust in and out with a harsh, fast rhythm, hitting that same spot over and over until Dean wasn't sure if he was crying out to beg him to stop or to beg him for more, more, more.

The fingers pulled out, leaving him suddenly bereft and he didn't know whether to cry out in relief or anguish, but then Cas had a hold of his hips and was angling his own cock at Dean's entrance.

With one quick thrust he was in and the second drove him to the hilt. Dean felt like he was being ripped apart from the inside but he bucked up into Castiel's every thrust, plunging him deeper, feeling the blunt tip hammer his prostate until he was so flooded with sensation he was aware of nothing else but their bodies moving in perfect unison. Dimly, he felt a hand curl around his cock and start jerking in tempo. Wet heat enveloped his mouth and a tongue thrust past his lips.

Cas pumped harder, faster and the pressure built so high Dean was certain he would explode before this was over.

But then Cas gave a short, sharp cry and liquid warmth flooded Dean's insides. The sensation was enough to send Dean hurtling over the edge himself; he screamed and his entire world flashed white.

When he came to Cas was still buried inside him and they were lying in a sticky mess that practically glued them together.

His heart pounded wildly and his breathing was erratic; he should have felt bliss but he was too busy freaking out because-

"What the hell just happened?"

Cas lifted his head a little and stared deep into Dean's panicked green eyes. "I already told you, Dean. I won't let Amara take you." He leaned in close until his lips were just barely grazing Dean's own. "You're mine."

It should have sounded like a sweet promise, but something in Castiel's voice had shifted.

It sounded like a threat.

Then Cas smiled and Dean realised that he didn't look anything like the Cas he knew and loved.

This wasn't right. This wasn't him.

Fear spiked in Dean's heart and he tried to push the angel off him but not-Cas had him pinned tight.

"Who the hell are you? What have you done with Cas?"

Not-Cas grinned. "I've taken up residence in my little brother's meat-suit for the time being, but don't worry, he's in here too. And rest assured; he thought you were a fabulous lay. He only wishes he'd had the idea first. He had no idea what a good little whore you would be for him."

Dean struggled to get free, only now comprehending just how strong angels really were. He was completely helpless – and _vulnerable._

"Lucifer," he whispered.

"In the flesh!" He spread Castiel's lips in a wide, feral smile. "And in yours. I meant what I said, you know, Dean. You're mine now. And pretty soon, Sam will be too."

He pulled out, clearly enjoying Dean's wince of discomfort. He climbed off the, waving a casual hand to keep Dean firmly in place when he tried to make a lunge for the angel blade he kept stashed under his mattress.

"Really, Dean, is that any way to treat your lover?"

Lucifer shook his head and used angel mojo to clean himself up. He looked down at his body, at Cas's body. "I can see the attraction," he said. "Let's do this again sometime. Catch you later, Dean-o." He flicked a casual salute and vanished.

Dean felt the pressure release from his limbs, but he couldn't move.

He lay in the mess of blood and sweat and semen, torn apart in more ways than one.

He stared up at the ceiling, unable to comprehend what had just happened, too overwhelmed to even think about the implications for the rest of the world now that Lucifer was free. He couldn't wonder why Cas had ever said yes, or even worry about what Lucifer might have planned for Sam.

He was wrecked. Ruined. He had finally worked out how he felt, and for a few minutes of insanity he had thought that he might actually be able to follow his heart and find that happily ever after.

But it was all a lie.

And now Cas was gone.


End file.
